The Mariinsky Opera's current tour schedule is nothing if not punishing. Their performance of Verdi's Requiem, their fourth concert in five days, was preceded by two of Wagner's Parsifal and one of Mahler's Eighth Symphony – both immensely taxing works. Listening to the Verdi, you couldn't help but wonder whether the strain was starting to show. It was patchy and perverse, in execution and interpretation. We've heard the Mariinsky on better form than this, while the Requiem itself has been much better done on numerous previous occasions.

In terms of the age-old debate about whether the work itself is devotional or dramatic, Valery Gergiev, as one might expect, favoured the latter approach, though his deepest insights were to be found in unusual places. The Kyrie, taken faster than most, was wonderfully urgent. The sense of numbed shock at Quantus Tremor Est Futurus was infinitely more disquieting than the batterings of the Dies Irae on either side of it. And the Sanctus was exemplary in its clarity and elation. Elsewhere, despite fine, shapely singing from the Mariinsky Chorus, too much of it felt routine, while some of the playing was curiously undistinguished.

The all-important soloists, meanwhile, were mixed. Tenor Sergey Semishkur sounded attractive, but couldn't, or wouldn't, sing softly in his upper registers on this occasion. Soprano Viktoria Yastrebova, a Flower Maiden in Parsifal the previous evening, was precarious in both tone and intonation, and had an intermittent habit of snuggling up towards notes from somewhere below them. So one was grateful to mezzo Olga Borodina and bass Ildar Abdrazakov, both rock-steady and fabulous, for providing us with the most memorable performances of a very variable evening.